The fusion kinases of ROS1 and ALK have been identified as oncogene drivers in small portions of many malignancies, especially in non-small cell lung cancer (NSCLC). ALK/ROS1/MET inhibitor crizotinib has been approved by the US Food and Drug Administration for the treatment of ALK or ROS1-positive non-small cell lung cancer in 2011 and 2016, respectively. The emergence of drug resistance presents a major issue for targeted therapy. Although ceritinib, alectinib, and brigatinib have been approved for crizotinib-refractory ALK+ patients with NSCLC, treatment options for patients with ROS1+ NSCLC are limited, especially for crizotinib-refractory patients. Ceritinib and entectinib demonstrated clinical efficacy only in crizotinib-naïve ROS1+ patients. The most common resistance mechanisms to crizotinib treatment in ROS1+ NSCLC is the solvent front mutation ROS1 G2032R and gatekeeper mutation ROS1 L2026M. TPX-0005, a novel three-dimensional macrocycle with a much smaller size than current ROS1 inhibitors in the clinic, was designed to overcome clinical resistance mutations systematically. TPX-0005 potently inhibited both wild type and mutant ROS1s including solvent front mutations and gatekeeper mutations. TPX-0005 showed pico-molar activity against ROS1 kinase (IC50 0.076 nM) in Reaction Biology kinase assay. The comparison of TPX-0005 with other ROS1 inhibitors in Ba/F3 cell proliferation assays is presented in the table. In the xenograft tumor model studies, TPX-0005 dramatically caused tumor regression in the tumors carrying WT or solvent-front mutated ROS1 fusion gene. Overall, TPX-0005 demonstrated desired drug-like properties, good safety profile, and is a supreme ROS1 inhibitor against WT and various mutated ROS1s. A phase 1/2 clinical trial of TPX-0005 is actively being pursued (NCT03093116).

 CD74-ROS1 Ba/F3 Cell Proliferation Assay IC50 (nM) 
Inhibitor WT G2032R D2033N L2026M S1986F S1986Y 
TPX-0005 <0.2 8.4 0.2 10 <0.2 <0.2 
Crizotinib 9.7 1402 139 606.4 20.9 19 
Lorlatinib 0.5 262.4 2.4 ND 0.3 0.3 
Entrectinib 25.4 2404 ND 2026 ND ND 
Ceritinib 131.9 2000 ND ND 14.2 26.9 
Brigatinib 28.6 1385 167.1 2115 27.7 24.6 
Cabozantinib 1.0 60.7 0.1 29.1 ND ND 
 CD74-ROS1 Ba/F3 Cell Proliferation Assay IC50 (nM) 
Inhibitor WT G2032R D2033N L2026M S1986F S1986Y 
TPX-0005 <0.2 8.4 0.2 10 <0.2 <0.2 
Crizotinib 9.7 1402 139 606.4 20.9 19 
Lorlatinib 0.5 262.4 2.4 ND 0.3 0.3 
Entrectinib 25.4 2404 ND 2026 ND ND 
Ceritinib 131.9 2000 ND ND 14.2 26.9 
Brigatinib 28.6 1385 167.1 2115 27.7 24.6 
Cabozantinib 1.0 60.7 0.1 29.1 ND ND 

ND: not determined.

Citation Format: J. Jean Cui, Dayong Zhai, Wei Deng, Evan Rogers, Zhongdong Huang, Jeffrey Whitten, John Lim, Yishan Li. TPX-0005, a supreme ROS1 inhibitor, overcomes crizotinib-resistant ROS1 mutations including solvent front mutation G2032R and gatekeeper mutation L2026M [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B185.